Closed-loop vectoring control of a turbulent jet using periodic excitation

Closed-loop control strategies were studied experimentally at low Reynolds and incompressible Mach numbers using periodic excitation to vector a turbulent jet. Vectoring was achieved by attaching a short, wide-angle diffuser at the jet exit and introducing periodic excitation from a slot covering one quadrant of the circumference of the round turbulent jet. Closed-loop control methods were applied to transition quickly and smoothly between different jet deflection angles. The frequency response of the zero-mass-flux piezoelectric actuator was flat to about 0.5 kHz, but the jet responds up to 30-50 Hz only. This is still an order of magnitude faster than conventional thrust vectoring mechanism. System identification procedures were applied to approximate the system's transfer function. A linear controller was designed that enabled fast and smooth transitions between stationary deflection angles and maintained desired jet vectoring angles under varying system conditions. The linear controller was tested over the entire range of available deflection angles, and its performance is evaluated and discussed.

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